(1) Field of the Invention
The present invention relates to an apparatus and a method for control rod exchange work during the regular inspection of a nuclear power plant using a boiling water reactor (referred to BWR), and more particularly an apparatus and a method for attaching or taking off a control rod (referred to CR), and for easily handling a fuel support piece (referred to FS).
(2) Description of the Prior Art
Conventionally, the spud coupling is used for connecting a CR and a control rod drive mechanism (referred to CRD) in a BWR. In the CR exchange work, such fittings as described in Japanese Patent Laid-Open No. 103399/1981 were presented.
However, in a BWR where the above-mentioned spud coupling is adapted, there is the possibility that the connection between a CR and a CRD is disconnected for some reason during plant operation. If such disconnection takes place during plant operation, normal power control become impossible and it is needed to shut down the plant operation.
The bayonet coupling is a way solving the above-mentioned problem of the CR-CRD disconnection. In the work of exchanging a CR to which the bayonet coupling is applied, a coupling socket, namely, a CR must be rotated by a predetermined angle for disconnecting the connection. Then, it is necessary to provide an apparatus for rotating a CR in the work of exchanging a CR to which the bayonet coupling is applied. A method for exchanging a CR to which the bayonet coupling is applied was proposed in Japanese Patent Laid-Open No. 205795/1990. In this method, after a FS is taken out above the upper grid plate by using an exclusive handling equipment for a FS, the CR is grasped by use of a CR handling apparatus attached to a fuel exchange apparatus, disconnected from the CRD by rotation and taken out above the upper grid plate by a subsidiary hoist of a fuel exchange apparatus. In attaching a new CR, the CR is connected to the CRD by using the above-mentioned CR handling apparatus in reverse procedures to the above-mentioned procedures and the FS is attached to a reactor core support plate by using an exclusive handling equipment for a FS. This prior art premises that the FS is taken out by the exclusive handling equipment for a FS. Therefore, in applying the prior art, many steps such as attaching or taking off the exclusive handling equipment for a FS and the CR handling apparatus to or from the subsidiary hoist, winching up or down the exclusive handling equipment for a FS and the control rod handling apparatus into or out of the reactor core and so forth are needed, which brings about much time consuming work.